Counting approximately 80,000 inhabitants in the seventeenth century, the town of Rouen was the second city of the kingdom of France. It comprised not only the most important Protestant community of Normandy, but also the largest number of foreign merchants. The Dutch merchants, who began around 1600 to replace the Flemish in Rouen, were particularly numerous among them. In the past, historians have been rather quick to consider all Dutch merchants as Protestants, but in reality there were quite a number of Catholics among them. In this article, I examine the relations between the Protestant and Catholic merchants of Dutch origin at Rouen, in particular their marriage strategy, the choice of godparents, and some contracts of commercial collaboration. The distance between the two confessions appears less profound than has been suggested before. Catholics were godparents for Protestant children, and mixed marriages were arranged among them. It is therefore clear that national solidarity played a greater role abroad than the confessional divisions did.